Neural Interface System

ABSTRACT

The neural interface system of the preferred embodiments includes an electrode array having a plurality of electrode sites and a carrier that supports the electrode array. The electrode array is coupled to the carrier such that the electrode sites are arranged both circumferentially around the carrier and axially along the carrier. A group of the electrode sites may be simultaneously activated to create an activation pattern. The system of the preferred embodiment is preferably designed for deep brain stimulation, and, more specifically, for deep brain stimulation with fine electrode site positioning, selectivity, tunability, and precise activation patterning. The system of the preferred embodiments, however, may be alternatively used in any suitable environment (such as the spinal cord, peripheral nerve, muscle, or any other suitable anatomical location) and for any suitable reason.

TECHNICAL FIELD

This invention relates generally to the neural interface field, and morespecifically to an improved neural interface system having an electrodearray with a series of electrode sites.

BACKGROUND

Chronic Deep Brain Stimulation (DBS) devices—‘brain pacemakers’—haveemerged in the last decade as a revolutionary new approach to thetreatment of neurological and psychiatric disorders. Conventional DBStherapy involves controllable electrical stimulation through a leadhaving four relatively large electrodes that are implanted in thetargeted region of the brain. While conventional DBS therapy isgenerally safe and effective for reducing cardinal symptoms of theapproved diseases, it often has significant behavioral and cognitiveside effects and limits on performance. Additionally, the therapeuticeffect is highly a function of electrode position with respect to thetargeted volume of tissue, and more specifically, a function of whichneuronal structures are influenced by the charge being delivered. Withconventional electrodes, there are limitations as to how the charge isdelivered and stimulation fields are limited as all of the electrodesites involved with stimulation are positioned along a single axis.Thus, there is a need for an improved neural interface system to providefine electrode positioning, selectivity, precise stimulation patterning,and precise lead location. This invention provides such an improved anduseful neural interface system.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic drawing of the neural interface system of apreferred embodiment.

FIG. 2 is a schematic drawing of the series of electrode arrays andguiding elements.

FIGS. 3A and 3B are schematic drawings of a first group of electrodesites and a first activation pattern and a second group of electrodesites and a second activation pattern respectively.

FIGS. 4A and 4B are schematic drawings of activation patterns andactivation intensities.

FIGS. 5A and 5B are schematic drawings of an activation pattern alongthe carrier and an activation around the carrier respectively.

FIG. 6 is a schematic drawing of excitation volumes along threedifferent dimensions of tissue.

FIG. 7 is a cross-sectional drawing of the silicone element, thecarrier, and the electrode array.

FIG. 8 is a photograph of ball bonds.

FIG. 9 is a photograph of the electrode array, the plurality ofelectrode sites, and the carrier.

FIG. 10 is a schematic drawing of the neural interface system implantedin a patient.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of preferred embodiments of the invention isnot intended to limit the invention to these embodiments, but rather toenable any person skilled in the art to make and use this invention.

As shown in FIG. 1, the neural interface system 10 of the preferredembodiments includes an electrode array 12 having a plurality ofelectrode sites 14. The electrode sites may be individually activated orsimultaneously activated as a group to create an activation pattern. Inalternative preferred embodiments, the neural interface may furtherinclude a carrier 16 that supports the electrode array. The electrodearray 12 is coupled to the carrier 16 such that the plurality ofelectrode sites 14 are arranged both circumferentially around thecarrier 16 and axially along the carrier 16. The system 10 of thepreferred embodiment is preferably designed for deep brain stimulation,and, more specifically, for deep brain stimulation with fine electrodesite positioning, selectivity, tunability, and precise activationpatterning. The system 10 of the preferred embodiments, however, may bealternatively used in any suitable environment (such as the spinal cord,peripheral nerve, muscle, or any other suitable anatomical location) andfor any suitable reason.

1. The Electrode Array

The electrode array 12 of the preferred embodiments functions tointerface with the tissue, or any other suitable substance, that it hasbeen implanted in or coupled to. The electrode array 12 includes aplurality of electrode sites 14 such that a group of the electrode sites14 may be simultaneously activated to create an activation pattern. Theelectrode array 12 provides the capability of incorporating feedbackcontrol through neural recordings for eventual on-demand stimulation.The electrode array 12 may further include fluidic channels providingthe capability to deliver therapeutic drugs, drugs to inhibit biologicresponse to the implant, or any other suitable fluid.

The electrode array 12 is preferably one of several variations. In afirst variation, the electrode array 12 is a planar array. In thisvariation, the electrode array 12 would be particularly useful forstimulation of surface tissue such as surface stimulation of the brainor spinal cord. In a second variation, the electrode array 12 has athree dimensional geometry. The geometry preferably has a circular orsemi-circular cross section, but may alternatively be any suitablegeometry with any suitable cross section such as a v-shaped crosssection. The planar electrode array 12 is preferably pre-formed into thethree dimensional geometry. This is preferably completed by positioningthe planar electrode array 12 in a mold and then placing the mold andelectrode array 12 in a furnace to be tempered, but may alternatively becompleted by any suitable process that alters the physical shape of theplanar substrate. The electrode array 12 in this variation, may bewrapped directly around the tissue to be stimulated such as a peripheralnerve or spinal cord. The electrode array 12 of the second variation maybe coupled to the carrier 16. The electrode array 12 is preferablycoupled to the carrier 16 such that the plurality of electrode sites 14are arranged both circumferentially around the carrier 16 and axiallyalong the carrier 16. Although the electrode array 12 is preferably oneof these variations, the electrode array 12 may be in any suitableconfiguration to interface with the tissue, or any other suitablesubstance, that it has been implanted in or coupled to.

The neural interface system 10 may include a single electrode array 12with a plurality of electrode sites 14 or may alternatively include aseries of electrode arrays 12, each with a plurality of electrode sites14. The neural interface system 10 may further include a guiding elementthat positions the series of electrode arrays 12 in a three dimensionalarrangement, or the electrode arrays 12 may alternatively be arranged ina three dimensional manner without an additional guiding element. Theneural interface system 10 may include one guiding element for everyelectrode array 12, such that the ratio of guiding elements to electrodearrays 12 is 1:1. Alternatively, the neural interface system 10 mayinclude one guiding element for every two or more electrode arrays 12,such that the ratio of guiding elements to first electrode arrays 12 isless than 1:1. Additionally, the guiding elements may be coupled to achamber 26, as shown in FIG. 2, or any other suitable element of theneural interface system 10 and may include a sharpened end adapted topenetrate the tissue and aid in the insertion of the electricalsubsystems and/or guiding elements into the tissue.

As shown in FIG. 2, the guiding element is preferably a rigid guidingelement 28. The guiding element may be a stylet, a guide tube, aconnector 34, or any other suitable guiding element. In this variation,the rigid guiding element 28 guides the electrode arrays 12 into athree-dimensional arrangement along predetermined trajectories. Therigid guiding elements 28 preferably implant the electrode arrays into aspecific location and a specific three-dimensional spatial distance fromone another determined by the location of the guiding elements 28. Forexample, as shown in FIG. 2, the guiding elements 28 are positioned at aspecific location and a specific three-dimensional spatial distance fromone another prior to implantation. Upon insertion of the rigid guidingelements 28 and the series of electrode arrays 12 the guiding elements28 will move the electrode arrays 12 along the predetermined trajectoryinto the corresponding specific location and three-dimensional spatialdistance from one another as the guiding elements 28. The trajectoriesare preferably parallel, but may alternatively be at any suitable angleto one another to implant the series of electrode arrays 12 into athree-dimensional arrangement. The material of the rigid guiding element28 is preferably a generally rigid material such as metal or plastic,but may alternatively be made from any suitable material.

2. The Plurality of Electrode Sites

The plurality of electrode sites 14 of the preferred embodimentsfunctions to electrically communicate with the tissue, or any othersuitable substance, that it has been implanted in or coupled to. Theelectrical communication is preferably a high-frequency, pulsed electriccurrent; electrical stimulation in monopolar, bipolar, tripolar, and/orquadrapolar modes; a recording of electrical signals; data transmission;and/or any other suitable electrical communication.

The plurality of electrode sites 14 can be activated individually or inselectable groups of electrode sites. The simultaneous activation of agroup of electrode sites 14 creates an activation pattern, generates anelectric field in the tissue medium having a spatial distribution ofcurrent density, and influences the pattern of neural excitation. Thiswill provide dynamic tunable electrical stimulation ranging frommacroscale activation, as shown in FIGS. 3A and 4A, to more selectivedirectional activation patterning using smaller groups of sites along oraround the carrier, as shown in FIGS. 3B and 4B. Additionally, each ofthe electrode sites 14 may be activated with an independent activationintensity. As shown in FIGS. 4A and 4B each activation intensity may beindividually distinct, or groups of electrode sites may each have thesame activation intensity.

As shown in FIGS. 5A and 5B, activation patterns from an electrode array12 can be translated not only axially up and down a carrier 16 (FIG.5A), but also side-to-side or circumferentially around the carrier 16(FIG. 5B) thus allowing for slight corrections in the position of theelectrode by electrical means. As shown in FIGS. 5A and 5B, theactivation patterns 36 and 38 (shown as isopotential contours) are eachcreated by the activation of two electrode sites 14. Noting thatcurvature and direction of curvature of isopotential surfaces indicatemagnitude and direction of second spatial derivative, the preferreddirection of excitation can be adjusted by the choice of sites activatedin an array. An activation pattern generates excitation volumes that arespecific for neural fibers or axons traveling in the three principledirections of the electrode array 12. As shown in FIG. 6, the excitationvolumes 40, 42, and 44 are generated by an activation pattern,specifically the activation pattern shown in FIG. 5A. The firstexcitation volume 40 is for axon orientation perpendicular to theelectrode and above it, the second excitation volume 42 is forvertically traveling axons, and the third excitation volume 44 is foraxons traveling parallel to the electrode.

As shown in FIGS. 3A and 3B, a group of the electrode sites aresimultaneously activated to create an activation pattern. As shown inFIG. 3A, activating a first group of electrode sites 18 creates a firstactivation pattern 20. The first group of electrode sites 18 includeseach of the electrode sites around the circumference of the carrier 16at a particular axial location. As shown in FIG. 3B, activating a secondgroup of electrode sites 22 creates a second activation pattern 24. Thesecond group of electrode sites 22 includes electrode sites at multipleaxial locations and less than each of the electrode sites around thecircumference of the carrier at a particular axial location.

The excitation of tissue surrounding an electrode site 14 is determinedby electrochemical properties of the individual electrode site and bygeometric properties of the entire electrode array and carrier assembly.For an electrode array 12 with several electrode sites 14 activatedsimultaneously, the activation pattern, and therefore the current flowsurrounding the electrode, is complex resulting in an equally complexpattern of tissue excitation. At a basic level, the spreading resistanceof an electrode site may determine the ability of the site to delivercharge to excitable tissue. When several electrode sites 14 on anelectrode array 12 are activated simultaneously there is an interactionof the electrode sites and activation patterns. For example, the secondactivation pattern, as shown in FIG. 3, may be modulated with theactivation of a third distinct group of electrode sites 14. Furthermore,multiple groups of activated electrode sites can be overlapping ornon-overlapping.

In one specific variation of the electrode array 12, as shown in FIG. 1,the electrode array 12 preferably includes sixty-four stimulationelectrode sites 30 and thirty-two recording electrode sites 32positioned circumferentially around and axially along the carrier 16.Each stimulation electrode site 30 has a surface area of preferably0.196 mm² (diameter=500 μm), but may alternatively have any suitablesurface area. Each recording electrode site 32 has a surface area ofpreferably 0.00196 mm² (diameter=50 μm), but may alternatively have anysuitable surface area. The stimulation electrode sites 30 are preferablypositioned such that four sites will be equally spaced around thecircumference of the carrier 16 (center-to-center spacing is about equalto 750 μm). Sites will also be preferably spaced at 750 μm in the axialdirection (center-to-center) and positioned at sixteen successivelocations. Between each row of stimulation electrode sites 30, tworecording electrode sites 32 will preferably be positioned on oppositesides of the carrier 16. The positions of each recording electrode sitepair will preferably shift ninety degrees between successive depths.Alternatively, there may be any suitable number of stimulation electrodesites 30 and recording electrode sites 32, and the stimulation electrodesites 30 and recording electrode sites 32 may alternatively bepositioned in any other suitable arrangement.

3 Fabrication of The Electrode Array and The Plurality of ElectrodeSites

The electrode array 12 is preferably made from a thin-film polymersubstrate (or any other suitable material) such that there is highdensity of electrode sites 14 at a first end of the array (the distalend) and bonding regions at a second end of the array (the proximalend). The proximal end is preferably thicker than the distal end of theelectrode array 12 to accommodate the bonding regions or the integrationof a second electrical subsystem. The polymer substrate is preferablyparylene or some combination of parylene and inorganic dielectrics, butmay alternatively be made out of any suitable material. The distal endof the array is preferably coupled to a carrier 16 to provide structuralsupport. Additionally, the distal end will be in direct contact with thetissue and so will preferably be made from suitable materials for bothbiocompatibility and dielectrics.

In general, the fabrication techniques for the electrode array 12 arepreferably similar to those used to create integrated circuits andtherefore preferably utilize similar substrate, conductor and insulatingmaterials. Fabrication of the electrode array 12 preferably starts on awafer substrate and the electrode sites 14 and additional features arepreferably added using a number of photolithographically patternedthin-film layers that are preferably defined by etching. The electrodearrays 12 produced in this manner are preferably reproducible,batch-processed devices that have features preferably defined to withinless than +/−1 μm. In addition, many of the fabrication techniques arepreferably compatible with the inclusion of an integrated flexibleribbon cable or connector 34 and a second electrical subsystem such ason-chip circuitry for signal conditioning and/or stimulus generation.

Polymer electrode arrays preferably include metal traces sandwichedbetween upper and lower layers of insulating polymer. One such polymeris parylene (parylene-C, Specialty Coating Systems, Indianapolis, Ind.,USA). The polymer is vapor phase deposited onto an oxidized siliconwafer that acts as a carrier. A layer of photoresist is then spun on andpatterned in preparation for metal lift-off. Layers of titanium andplatinum are preferably next deposited and patterned using lift-off. Thetop layer of polymer is then vapor phase deposited. The wafers are thenpreferably patterned and dry-etched to form the final electrode shapeand create openings to the underlying metal. These metal surfaces formthe electrode sites and additional features such as conductiveinterconnects and bond pads. HF dissolution of the oxide release layeris used to remove the devices from the wafer. The devices are finallycleaned using multiple soaks and rinses in DI water. Presently, theprocess requires only two photolithographic masks resulting in rapidturn-around for easy design iteration.

The electrode sites 14 are preferably patterned directly onto thepolymer substrate. The electrode sites 14 are preferably metal such asiridium, platinum, gold, but may alternatively be any other suitablematerial. Iridium oxide is preferably used for the electrode sites 14due to its high charge capacity (3 mC/cm²). The targeted chargeinjection limit for the activation pattern 46 as shown in FIG. 4A ispreferably 500 nC/cm², while preferably maintaining a safe chargedensity of 30 μC/cm². The targeted composite impedance (electrodecontact plus lead) is preferably 10 kΩ (stimulating contacts) and 100 kΩ(recording contacts). Impedance matching will preferably occur acrossall sites. Each site will preferably be electrically isolated withcross-talk preferably below 1%.

The electrode array 12 preferably further includes conductiveinterconnects disposed between layers of dielectrics that insulate theinterconnects on top and bottom sides. Preferably a group of theconductive interconnects terminate with electrode sites 14 on the distalend and/or with bond pads for electrical connection to externalinstrumentation and/or hybrid chips on the proximal end. The conductiveinterconnects are preferably metal or polysilicon, but may alternativelybe any other suitable material. Polyimide, parylene, inorganicdielectrics, or a composite stack of silicon dioxide and silicon nitrideis preferably used for the dielectrics, however any other suitablematerials may alternatively be used.

The conductive interconnects are preferably made as wide as possible toreduce the resistance. The conductive interconnects will vary in lengthas they terminate at different locations, and so in order to equalizethe resistance across all leads, the line widths are preferably adjustedaccordingly. These conductive interconnects, as well as the connectionswill be preferably buried in silicone and thus not be at risk toleakage, as shown in FIG. 1D. The electrode array 12 will function moreefficiently if all the impedances of the conductive interconnects areequal as seen from the bonding area. This is preferably accomplished byincreasing the width of the longer traces. Preferably, the width of eachsegment of each conductive interconnect is optimized using a “hillclimbing” method. A layout program preferably generates polygonsrepresenting the several conductive interconnects.

4. The Carrier

The carrier 16 of the preferred embodiments, as shown in FIG. 9,functions to support the electrode array 12. The carrier 16 may furtherfunction to shuttle the electrode array 12 into tissue or othersubstances. The shape of the carrier 16 is preferably tubular with abouta 1-mm diameter, but may alternatively be any suitable shape of anysuitable diameter for the desired functions. The carrier 16 may includea sharpened end adapted to penetrate the tissue and aid in the insertionof the carrier 16 and the electrode array 12 into the tissue. Thecarrier 16 may further extend the functionality of the system byproviding fluidic channels through which therapeutic drugs, drugs toinhibit biologic response to the implant, or any other suitable fluidmay be transmitted. This provides for the precise delivery of specificpharmaceutical compounds to localized regions of the body, such as thenervous system, and could facilitate, for example, intraoperativemapping procedures or long-term therapeutic implant devices. The fluidicchannels may also provide a location through which a stiffener or styletmay be inserted to aid with implantation. Alternatively, the carrier 16may further include a separate lumen through which the stiffener orstylet may be inserted.

The carrier 16 is preferably one of several variations. In a firstvariation, the carrier 16 is a polymeric carrier 16. The carrier 16 ispreferably made of a polymer such as polyimide or silicone, but may bealternatively made from any other suitable material. The carrier 16 ispreferably flexible, but may alternatively be rigid or semi rigid. In asecond variation, the carrier 16 is a metal carrier. The carrier in thisvariation may be a solid metal tube or cylinder, or it may alternativelybe perforated or not solid in any other suitable fashion. In a thirdvariation, the carrier 16 is resorbable carrier 16, which is resorbedinto tissue after a period of time, and upon resorption, the electrodearray 12 will be left to float freely in the brain or other suitabletissue or material. The resorbable carrier 16 is preferably made ofimplantable medical fabric woven or knitted from a bioresorbablepolymer. The bioresorbable polymer is preferably polyglycolide orpolylactide, but may alternatively be made from any suitablebioresorbable material. Although the carrier 16 is preferably one ofthese three variations, the carrier 16 may be any suitable element toshuttle the electrode array 12 and the connector 34 into tissue or othersubstances and provide structural support.

5. The Second Electrical Subsystem and the Connector

Additionally, the system 10 may further include a second electricalsubsystem. The second electrical subsystem of the preferred embodimentsfunctions to operate with the electrode array 12. The second electricalsubsystem may include multiple different electrical subsystems or aseries of the same subsystems. The second electrical subsystem may beintegrated into the proximal end of the electrode array 12 or may becoupled to the electrode array 12 via a connector 34 as described below.The second electrical subsystem is preferably at least one of severalvariations of suitable electronic subsystems to operate with theelectrode array 12 or any combination thereof The second electricalsubsystem may be a printed circuit board with or without on-boardintegrated circuits and/or on-chip circuitry for signal conditioningand/or stimulus generation, an Application Specific Integrated Circuit(ASIC), a multiplexer chip, a buffer amplifier, an electronicsinterface, an implantable pulse generator (produces a high-frequency,pulsed electric current), an implantable rechargeable battery,integrated electronics for either real-time signal processing of theinput (recorded) or output (stimulation) signals, integrated electronicsfor control of the fluidic components, any other suitable electricalsubsystem, or any combination thereof. In one specific variation, asshown in FIG. 10, the neural interface system 10 includes an electrodearray 12, an electronics interface 56 and implantable pulse generatorlocated in a cranial burr-hole chamber, and an implantable rechargeablebattery 58. Although the second electrical subsystem is preferably oneof these several subsystems, the second electrical subsystem may be anysuitable element or combination of elements to operate the electrodearray 12.

Additionally, the system 10 may further include a connector 34. Theconnector 34 of the preferred embodiments functions to couple theelectrode array 12 to the second electrical subsystem. The connector 34is preferably one of several variations. As shown in FIG. 1, theconnector 34 is preferably a flexible ribbon cable. The ribbon cable ispreferably polymer ribbon cable, but may alternatively be any othersuitable ribbon cable. The connector 34 may alternatively be anysuitable element to couple the electrode array 12 to the secondelectrical subsystem, such as wires, conductive interconnects, etc.

The ribbon cable may be encased in silicone or any other suitablematerial, as shown in FIGS. 1D and 7A. In some situations, theelectrical subsystem may have multiple ribbon cables. Preferably,multiple ribbon cables would be physically attached along their entirelength, using a suitable adhesive such as medical grade adhesive or anyother suitable connection mechanism. The cable is preferably connectedto the electrical subsystems through rivet bonds, ball bonds, or anyother suitable connection mechanisms. The connector 34 may alternativelybe seamlessly manufactured with the first and or second electricalsubsystem. The connector 34 may further include fluidic channels adaptedto deliver therapeutic drugs, drugs to inhibit biologic response to theimplant, or any other suitable fluid.

6. The Stylet and the Guide Tube

Additionally, the system 10 may further include a stylet. The stylet ofthe preferred embodiments functions to penetrate the tissue or othermaterial and/or functions to provide structural support to the systemduring implantation. The stylet is preferably inserted into a lumen of acarrier 16, but may alternatively be located and inserted into anysuitable component of the system in any suitable manner. The stylet mayinclude a sharpened end adapted to penetrate the tissue and aid in theinsertion of the stylet, the carrier 16, and/or the electrode array 12into the tissue. The stylet is preferably removed from the tissuefollowing the placement of the electrode array 12, but may alternativelybe adapted to remain in the tissue while still allowing the implantedelectrode array 12 to float freely in the brain. This may beaccomplished by the stylet being selectively flexible (throughelectrical stimulus or other suitable method) or by being resorbableinto the tissue after a period of time. The stylet is preferably madefrom a stiff material such as metal, but may alternatively be made fromany suitable material. In one variation, the metal is preferablyinsulated metal wire. In this variation, the insulated metal wire maynot have insulation covering a sharpened tip, and thus can be used as aconventional single-channel microelectrode.

Additionally, the system 10 may further include a guide tube. The guidetube of the preferred embodiments functions to facilitate the insertionof the electrode array 12 and/or functions to provide structural supportto the system during implantation. The guide tube may be further adaptedto allow the electrode array 12 to move freely in the tissue, allowingthe placement of the electrode array 12 without disconnecting the secondelectrical subsystem. The guide tube is preferably made of a rigidmaterial, which can be inserted into tissue or other substances withoutbuckling and can maintain a generally straight trajectory through thetissue. The material may be uniformly rigid, or rigid only in aparticular direction (such as the axial direction). The material ispreferably plastic such as a medical grade plastic, but mayalternatively be any suitable material such as metal or a combination ofmaterials. The guide tube may further include a sharpened end adapted topenetrate the tissue and aid in the insertion of the guide tube into thetissue. The guide tube may also include alignment and or fixationfeatures to facilitate positioning and stabilizing the series ofelectrode array 12 in the tissue, particularly during removal of theguide tube.

7. Other Aspects of the Invention

As shown in FIG. 1, the neural interface system 10 of the preferredembodiments includes an electrode array 12 having a plurality ofelectrode sites 14 and a carrier 16 that supports the electrode array.The electrode array 12 is coupled to the carrier 16 such that theplurality of electrode sites 14 are arranged both circumferentiallyaround the carrier 16 and axially along the carrier 16. In one preferredembodiment, the electrode array 12 preferably includes both recordingelectrode sites 32 and stimulation electrode sites 30, as shown in FIG.1A. In this preferred embodiment, the electrode array 12 furtherincludes interconnects 48 ascending from the electrode array 12, asshown in FIG. 1B. The interconnects 48 transition from the outer surfaceof the carrier 16 into the core such that the connection point and theentire connector 34 are imbedded in silicone, as shown in FIG. 1B. Tofacilitate adhesion between the silicone and polymer, smallnon-homogeneous perforations are preferably micromachined in the polymersubstrate to allow for liquid silicone to flow into and form a robustanchor after being cured. The electrode array 12 is preferably connectedto the connector 34 via the interconnects 48, as shown as FIG. 1C.

The electrode array 12 and carrier 16 are preferably assembled by amethod, as shown in FIG. 7, including any of the following steps, anysuitable additional steps, and any combination of steps thereof.

-   -   Connecting electrode array 12 to the connector 34. This is        preferably completed with ball bonds 52, as shown in FIG. 8, but        may alternatively include any other suitable technique. “Rivet”        bonds bonding technique involves ball bonding through a hole in        the polymer cable that is surrounded by an annular bond pad, to        a bond pad on the device underneath. This effectively forms a        rivet that connects the two devices both electrically and        mechanically, as shown in FIG. 8.    -   Connecting a second electrical subsystem such as a flexible        printed circuit board (PCB) to the connector 34. This is        preferably completed with wire-bonds bonded to bond pads on the        connector 34, but may alternatively include any other suitable        technique.    -   Pre-forming the electrode array 12. The planar electrode array        12 will be preferably pre-formed into a 3-dimensional        cylindrical form, or any other suitable form to be compatible        with the carrier 16. This step is preferably completed by        positioning the planar electrode array 12 in a mold and then        placing the mold and electrode array 12 in a furnace to be        tempered, but may alternatively be completed by any suitable        process that alters the physical shape of the planar substrate.    -   Connecting the interconnects 48. In some variations, there may        be two interconnects 48 such as ribbon cables ascending from the        electrode array 12, as shown in FIG. 1B. These two interconnects        48 are preferably connected along their entire length, to form a        connector 34, using a medical grade adhesive, or any other        suitable connection mechanism.    -   Injection molding the silicone element 50, as shown in FIG. 7.        This is preferably completed by providing an injection mold tool        that provides for the placement of the connector 34 and        connections within it, as shown in FIG. 7A, and then liquid        medical grade silicone will be preferably injected into the mold        and thermally cured. The carrier 16 may be the distal portion of        the silicone element 50, as shown in FIG. 7B, wherein the        electrode array 12 is wrapped around the carrier 16.        Additionally, a tube may be embedded in the silicone and will        act as a stylet passage 54. The tube is preferably made of a        polymer such as PTFE or any other suitable material with a low        coefficient of friction.

A method of implanting an neural interface system 10, as shown in FIG.10, preferably comprises any combination of the following steps (or anyother suitable steps):

-   -   attaching the chamber 26 to the scull (preferably in a cranial        burr-hole) of a patient;    -   implanting, through the guide tube and/or with a stylet, an        electrode array 12 coupled via a connector 34 to a second        electrical subsystem;    -   removing the guide tube over the second electrical subsystem        and/or removing the stylet;    -   placing the second electrical subsystem within the chamber 26;        and    -   sealing the electrical subsystems within the chamber 26.

Although omitted for conciseness, the preferred embodiments includeevery combination and permutation of the various electrode arrays, thevarious carriers, the various electrical subsystems and connectors, andthe various guide tubes and stylets.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

1. A neural interface system, comprising: an electrode array having aplurality of electrode sites that electrically communicate with theirsurroundings; wherein the plurality of electrode sites includes a subsetof stimulation electrode sites and a subset of recording electrodesites; and a carrier that supports the electrode array; wherein theelectrode array is coupled to the carrier such that the plurality ofelectrode sites are arranged both circumferentially around the carrierand axially along the carrier.
 2. The neural interface system of claim 1further including a second electrode array having a second plurality ofelectrode sites that electrically communicate with their surroundingsand a second carrier that supports the second electrode array.
 3. Theneural interface system of claim 2 further including a guiding elementthat positions the electrode arrays in a three dimensional arrangement.4. The neural interface system of claim 1 wherein there the subset ofstimulation electrode sites includes at least thirty-two stimulationelectrode sites and the subset of recording electrode sites includes atleast sixteen recording electrode sites.
 5. The neural interface systemof claim 4 wherein the subset of stimulation electrode sites arepositioned such that at least two sites are spaced around thecircumference of the carrier at each axial location and such that atleast eight sites are spaced along the axis of the carrier at eachcircumferential location, and wherein at least two recording electrodesites are located between each row of stimulation electrode sites andare positioned on opposite sides of the carrier from one another.
 6. Theneural interface system of claim 1 wherein the carrier is cylindrical.7. The neural interface system of claim 6 wherein the carrier furtherincludes fluidic channels adapted to transmit fluid.
 8. The neuralinterface system of claim 1 wherein the carrier is a flexible polymer.9. The neural interface system of claim 1 further including a secondelectrical subsystem that operates with the electrode.
 10. The neuralinterface system of claim 9 further including a connector that couplesthe electrode array to the second electrical subsystem.
 11. The neuralinterface system of claim 10 wherein the connector is a polymer ribboncable.
 12. The neural interface system of claim 10 wherein the connectorfurther includes fluidic channels adapted to transmit fluid.
 13. Theneural interface system of claim 1 wherein the electrode array is madefrom a thin-film substrate and the plurality of electrode sites islocated at a first end of the electrode array and bonding regions arelocated at a second end of the electrode array, wherein conductiveinterconnects couple the plurality of electrode sites on the first endof the electrode array to the bonding regions on the second end of theelectrode array.
 14. The neural interface system of claim 13 wherein theelectrode array further includes metal traces positioned between a firstlayer of polymer and a second layer of polymer, wherein the metal tracesinclude the plurality of electrode sites, the bonding regions, andconductive interconnects.
 15. The neural interface system of claim 14wherein the conductive interconnects are adapted such that the width ofthe conductive interconnect is proportional to the length of theconductive interconnect, such that the resistance is generally equalacross all conductive interconnects.
 16. A method of creating a patternof tissue medium excitation comprising the steps of: providing anelectrode array having a plurality of electrode sites that electricallycommunicate with their surroundings; simultaneously activating of agroup of electrode sites and thereby creating an activation pattern;generating an electric field in the tissue medium having a spatialdistribution of current density; and influencing the pattern of tissuemedium excitation.
 17. The method of claim 16 wherein each of theelectrode sites are activated with an independent activation intensity.18. The method of claim 17 wherein a first activation pattern is createdby activating a first group of electrode sites, wherein the first groupof electrode sites includes each of the electrode sites around thecircumference of the carrier at a particular axial location.
 19. Themethod of claim 17 wherein a second activation pattern is created byactivating a second group of electrode sites, wherein the second groupof electrode sites includes electrode sites at multiple axial locationsand less than each of the electrode sites around the circumference ofthe carrier at a particular axial location.
 20. The neural interfacesystem of claim 19, wherein the second activation pattern is modulatedwith the activation of a third group of electrode sites.
 21. A method ofassembling a neural interface system comprising the steps of: providinga electrode array having a plurality of electrode sites thatelectrically communicate with their surroundings; providing a connector;connecting the electrode array to the connector; and injection molding asilicon element having an end portion; wherein the silicon elementencases the connector and the end portion of the silicon element iscoupled to the electrode array.
 22. The method of claim 21 wherein theelectrode array is a planar electrode array and the method furthercomprises the step of pre-forming the planar array into a 3-dimensionalform.
 23. The method of claim 22 wherein the step of pre-forming theplanar array into a 3-dimensional form is accomplished by the steps ofpositioning the planar electrode array in a mold and tempering the moldand electrode array.
 24. A neural interface system, comprising: anelectrode array having a plurality of electrode sites that electricallycommunicate with their surroundings; wherein the plurality of electrodesites includes a subset of at least thirty-two stimulation electrodesites and a subset of at least sixteen recording electrode sites; and acarrier that supports the electrode array; wherein the electrode arrayis coupled to the carrier such the subset of stimulation electrode sitesare positioned such that at least two sites are spaced around thecircumference of the carrier at each axial location and such that atleast eight sites are spaced along the axis of the carrier at eachcircumferential location, and wherein at least two recording electrodesites are located between each row of stimulation electrode sites andare positioned on opposite sides of the carrier from one another.